SRC/clantb.f(3)

NAME
SRC/clantb.f

SYNOPSIS

  Functions/Subroutines
real function clantb (norm, uplo, diag, n, k, ab, ldab, work)
CLANTB returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a triangular band matrix.

Function/Subroutine Documentation

  real function clantb (character norm, character uplo, character diag, integer n, integer k, complex, dimension( ldab, * ) ab, integer ldab, real, dimension( * ) work)

CLANTB returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a triangular band matrix.

Purpose:

    !>
    !> CLANTB  returns the value of the one norm,  or the Frobenius norm, or
    !> the  infinity norm,  or the element of  largest absolute value  of an
    !> n by n triangular band matrix A,  with ( k + 1 ) diagonals.
    !>

Returns
    CLANTB

    !>
    !>    CLANTB = ( max(abs(A(i,j))), NORM = 'M' or 'm'
    !>             (
    !>             ( norm1(A),         NORM = '1', 'O' or 'o'
    !>             (
    !>             ( normI(A),         NORM = 'I' or 'i'
    !>             (
    !>             ( normF(A),         NORM = 'F', 'f', 'E' or 'e'
    !>
    !> where  norm1  denotes the  one norm of a matrix (maximum column sum),
    !> normI  denotes the  infinity norm  of a matrix  (maximum row sum) and
    !> normF  denotes the  Frobenius norm of a matrix (square root of sum of
    !> squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.
    !>

Parameters
    NORM

    !>          NORM is CHARACTER*1
    !>          Specifies the value to be returned in CLANTB as described
    !>          above.
    !>

    UPLO

    !>          UPLO is CHARACTER*1
    !>          Specifies whether the matrix A is upper or lower triangular.
    !>          = 'U':  Upper triangular
    !>          = 'L':  Lower triangular
    !>

    DIAG

    !>          DIAG is CHARACTER*1
    !>          Specifies whether or not the matrix A is unit triangular.
    !>          = 'N':  Non-unit triangular
    !>          = 'U':  Unit triangular
    !>

    N

    !>          N is INTEGER
    !>          The order of the matrix A.  N >= 0.  When N = 0, CLANTB is
    !>          set to zero.
    !>

    K

    !>          K is INTEGER
    !>          The number of super-diagonals of the matrix A if UPLO = 'U',
    !>          or the number of sub-diagonals of the matrix A if UPLO = 'L'.
    !>          K >= 0.
    !>

    AB

    !>          AB is COMPLEX array, dimension (LDAB,N)
    !>          The upper or lower triangular band matrix A, stored in the
    !>          first k+1 rows of AB.  The j-th column of A is stored
    !>          in the j-th column of the array AB as follows:
    !>          if UPLO = 'U', AB(k+1+i-j,j) = A(i,j) for max(1,j-k)<=i<=j;
    !>          if UPLO = 'L', AB(1+i-j,j)   = A(i,j) for j<=i<=min(n,j+k).
    !>          Note that when DIAG = 'U', the elements of the array AB
    !>          corresponding to the diagonal elements of the matrix A are
    !>          not referenced, but are assumed to be one.
    !>

    LDAB

    !>          LDAB is INTEGER
    !>          The leading dimension of the array AB.  LDAB >= K+1.
    !>

    WORK

    !>          WORK is REAL array, dimension (MAX(1,LWORK)),
    !>          where LWORK >= N when NORM = 'I'; otherwise, WORK is not
    !>          referenced.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 139 of file clantb.f.

Author

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